The present invention relates to a rotary rolling piston compressor with a fixed vane, and more specifically to a new construction for the vane of this type of compressor.
In rotary rolling piston type compressors the fixed sliding vane does the separation of two chambers in the interior of the cylinder, a suction chamber at low pressure and a high pressure chamber or a discharge one. This separation is obtained as the vane top end follows the rolling piston movement under the influence of a biasing member. Due to the fact of separating two chambers with great pressure difference, the vane is forced against the sliding slot surface by the high pressure side. This causes problems of metallic contact and wear between the vane and the sliding slot.
One of the known solutions tries to reduce this problem through the improvement of the vane lubricating system, especially where the metallic contact occurs. This is the case of the U.S. Pat. No. 4,629,403 (TECUMSEH).
Another attempt is to reduce the pressure difference between the chambers at the end of the compression cycle is shown in U.S. Pat. No. 4,664,608 (G.E.).
Although these solutions reduce the problem of the wear between the vane and the sliding slot, they give rise to losses of volumetric efficiency of the compressor.
In the first above-mentioned solution (U.S. Pat. No. 4,629,403), the placing of a lubricating hole with oil at high pressure, connected to the low pressure or suction chamber through the clearance for the sliding of the vane at the slot, causes the leakage of this oil to the interior of the cylinder. This increases the fluid refrigerant temperature in the suction chamber, reducing its volumetric efficiency.
According to the first solution, the aim is to reduce the wear between the vane and the slot through the provision of lubrication in the places where the wear of the parts occurs. However, in spite of reducing the problem of wear between the vane and the slot, this first solution requires a lubricating oil flow in a volume that becomes prejudicial to the compressor efficiency because it leaks into the suction chamber during a large part or all of the compression cycle resulting in the inadequate heating of the fluid refrigerant.
On the second solution the opening of the orifice for the pressure release will always take place at a given rotation angle of the crankshaft, whether the discharge pressure has been reached inside the cylinder or not, which depends on the operational condition in which the compressor is applied. This may cause backflow of the refrigerant gas already discharged in the housing back to the interior of the cylinder. This obviously adversely affects the energy and volumetric efficiency of the compressor.